I do not believe Rains had anything to do with the development of the coal torpedo. Of course, I have a certain bias. However, an earlier version of the coal torpedo, that is hollow pieces of firewood filled with explosives, was in use in the Trans-Mississippi by Courtenay as early as August, 1863. Courtenay received endorsements of his plan from Gen. Pike and Gen. Price, and traveled to Richmond to explain his plan to Pres. Davis. His letter to Davis is endorsed with instructions to the ordnance bureau to prepare some castings and make experiment with them. I think that's pretty strong evidence that Courtenay came up with the idea. Later, Rains described them in his notebooks, but that was long after they were already in use.